Inflammation and Alzheimer's disease.

Chemoprevention refers to the use of agents to inhibit, reverse or retard tumorigenesis. Numerous phytochemicals derived from edible plants have been reported to interfere with a specific stage of the carcinogenic process. Many mechanisms have been shown to account for the anticarcinogenic actions of dietary constituents, but attention has recently been focused on intracellular-signalling cascades as common molecular targets for various chemopreventive phytochemicals.

Cancer chemoprevention with dietary phytochemicals

This report describes a number of substructural features which can help to identify compounds that appear as frequent hitters (promiscuous compounds) in many biochemical high throughput screens. The compounds identified by such substructural features are not recognized by filters commonly used to identify reactive compounds. Even though these substructural features were identified using only one assay detection technology, such compounds have been reported to be active from many different assays. In fact, these compounds are increasingly prevalent in the literature as potential starting points for further exploration, whereas they may not be.

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New Substructure Filters for Removal of Pan Assay Interference Compounds (PAINS) from Screening Libraries and for Their Exclusion in Bioassays

▪ Abstract The prostaglandin endoperoxide H synthases-1 and 2 (PGHS-1 and PGHS-2; also cyclooxygenases-1 and 2, COX-1 and COX-2) catalyze the committed step in prostaglandin synthesis. PGHS-1 and 2 are of particular interest because they are the major targets of nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2 inhibitors. Inhibition of the PGHSs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of these enzymes relate mechanistically to cyclooxygenase and peroxidase catalysis, and how differences in the structure of PGHS-2 confer on this isozyme differential sensitivity to COX-2 inhibitors. We further examine the evidence for independent signaling by PGHS-1 and PGHS-2, and the complex mechanisms for regulation of PGHS-2 gene expression.

Cyclooxygenases: Structural, cellular, and molecular biology

Elevated rates of reactive oxygen species (ROS) have been detected in almost all cancers, where they promote many aspects of tumour development and progression. However, tumour cells also express increased levels of antioxidant proteins to detoxify from ROS, suggesting that a delicate balance of intracellular ROS levels is required for cancer cell function. Further, the radical generated, the location of its generation, as well as the local concentration is important for the cellular functions of ROS in cancer. A challenge for novel therapeutic strategies will be the fine tuning of intracellular ROS signalling to effectively deprive cells from ROS-induced tumour promoting events, towards tipping the balance to ROS-induced apoptotic signalling. Alternatively, therapeutic antioxidants may prevent early events in tumour development, where ROS are important. However, to effectively target cancer cells specific ROS-sensing signalling pathways that mediate the diverse stress-regulated cellular functions need to be identified. This review discusses the generation of ROS within tumour cells, their detoxification, their cellular effects, as well as the major signalling cascades they utilize, but also provides an outlook on their modulation in therapeutics.

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Reactive oxygen species in cancer

Inflammatory diseases such as asthma and rheumatoid arthritis are characterised at the molecular level by chronically increased expression of multiple cytokines, chemokines, kinins and their receptors, adhesion molecules, and inflammatory enzymes such as inducible nitric oxide synthase (iNOS) and the inducible cyclooxygenase (COX-2).1 At the cellular level, inflamed regions show a substantial influx of various inflammatory cells, arterial dilation, increased blood flow, plasma protein leakage, and oedema whilst, in the case of chronic asthma, substantial remodelling of the airways is observed involving excessive smooth muscle proliferation. However, these parameters of inflammation are effectively reduced by treatment with glucocorticoids by both direct and indirect mechanisms.2 3 For example, the reduced eosinophilia following glucocorticoid treatment in asthmatic subjects arises by direct promotion of eosinophil apoptosis and indirectly by suppressing receptor expression and production of cytokines or growth factors.4 These include factors such as interleukin (IL)-3, IL-5, granulocyte-macrophage colony stimulating factor (GM-CSF), and eotaxin which are involved in eosinophil maturation, recruitment, and survival. Similarly, glucocorticoids reduce T cell proliferation and increase T cell apoptosis via mechanisms that are at least partly the result of inhibition of the T cell growth factor, IL-2.5-8 Likewise, monocyte apoptosis is increased and influx of other infiltrating inflammatory cells is also repressed.2 9 Again, this is partly caused by reduced expression of adhesion molecules, both on migrating and target cells, as well as reduced expression of cytokines and chemokines from sites of inflammation.

Therapeutically, the ability to suppress a number of inflammatory indices makes glucocorticoids among the most potent anti-inflammatory agents currently available for the treatment of chronic inflammatory diseases such as asthma.2 3 The clinical efficacy of synthetic glucocorticoids such as prednisolone or dexamethasone stems from their ability to mimic natural glucocorticosteroids. Bodily insults, including inflammation, pain, infection or even mental …

https://thorax.bmj.com/content/thoraxjnl/55/7/603.full.pdf

Molecular mechanisms of glucocorticoid action: what is important?

Evidence for Involvement of NF-κB in the Transcriptional Control of COX-2 Gene Expression by IL-1β ☆

Resveratrol (3,4',5-trihydroxystilbene) is a polyphenolic stilbene found in the skins of red fruits, including grapes, that may be responsible for some of the health benefits ascribed to consumption of red wine. Resveratrol has been shown to have antioxidant properties and can act as an estrogen agonist. This study examined the anti-inflammatory effects of resveratrol on human airway epithelial cells. Resveratrol and the related molecule quercetin, but not deoxyrhapontin, inhibited IL-8 and granulocyte-macrophage colony-stimulating factor release from A549 cells. Neither the estrogen receptor antagonist tamoxifen nor the glucocorticoid antagonist mifepristone altered the inhibitory effect of resveratrol. The mechanism of resveratrol action was investigated further using luciferase reporter genes stably transfected into A549 cells. Resveratrol and quercetin inhibited NF-kappaB-, activator protein-1-, and cAMP response element binding protein-dependent transcription to a greater extent than the glucocorticosteroid dexamethasone. These compounds also had no significant effect on acetylation or deacetylation of core histones. Resveratrol, but not estradiol or N-acetyl cysteine, inhibited cytokine-stimulated inducible nitric oxide synthase expression and nitrite production (IC50 = 3.6 +/- 2.9 microM) in human primary airway epithelial cells. Resveratrol also inhibited granulocyte-macrophage colony-stimulating factor release (IC50 = 0.44 +/- 0.17 microM), IL-8 release (IC50 = 4.7 +/- 3.3 microM), and cyclooxygenase-2 expression in these cells. This study demonstrates that resveratrol and quercetin have novel nonsteroidal anti-inflammatory activity that may have applications for the treatment of inflammatory diseases.

Anti-inflammatory Effects of Resveratrol in Lung Epithelial Cells: Molecular Mechanisms

Glucocorticoids (corticosteroids) are highly effective in combating inflammation in the context of a variety of diseases. However, clinical utility can be compromised by the development of side effects, many of which are attributed to the ability of the glucocorticoid receptor (GR) to induce the transcription of, or transactivate, certain genes. By contrast, the anti-inflammatory effects of glucocorticoids are due largely to their ability to reduce the expression of pro-inflammatory genes. This effect has been predominantly attributed to the repression of key inflammatory transcription factors, including AP-1 and NF-kappaB, and is termed transrepression. The ability to functionally separate these transcriptional functions of GR has prompted a search for dissociated GR ligands that can differentially induce transrepression but not transactivation. In this review, we present evidence that post-transcriptional mechanisms of action are highly important to the anti-inflammatory actions of glucocorticoids. Furthermore, we present the case that mechanistically distinct forms of glucocorticoid-inducible gene expression are critical to the development of anti-inflammatory effects by repressing inflammatory signaling pathways and inflammatory gene expression at multiple levels. Considerable care is therefore required to avoid loss of anti-inflammatory effectiveness in the development of novel transactivation-defective ligands of GR.

https://molpharm.aspetjournals.org/content/molpharm/early/2007/07/10/mol.107.038794.full.pdf

Separating Transrepression and Transactivation: A Distressing Divorce for the Glucocorticoid Receptor?

Human labour is associated with the up-regulation of prostaglandins within the uterus, synthesized via the type-2 cyclo-oxygenase enzyme (COX-2). These lead to remodelling of the fetal membranes and cervix and to stimulation of myometrial contractions. In the human, the principal source of prostaglandins is the amnion. Progesterone acts to promote myometrial quiescence, and in many species the onset of labour is preceded by withdrawal of progesterone. Humans show no systemic progesterone withdrawal, although biochemical changes within the uterus are similar to those in other species. A mutual negative interaction between the transcription factor nuclear factor (NF)-kappaB and the progesterone receptor (PR) has been reported. Using transient transfections and assays for transcriptional activation and promoter binding, we have shown that there is constitutive activity of NF-kappaB in amnion cells at the time of labour, and that COX-2 expression depends upon NF-kappaB. In cells obtained before labour, in which NF-kappaB activity is low, increasing the concentration of PR represses NF-kappaB dependent transcription, while stimulation with IL-1beta both increases NF-kappaB activity and represses PR activity. Our data suggest that human labour is associated with constitutive NF-kappaB activity within the amnion, which functions to increase the expression of COX-2 and appears to contribute to the 'functional progesterone withdrawal'.

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Human labour is associated with nuclear factor-κB activity which mediates cyclo-oxygenase-2 expression and is involved with the ‘functional progesterone withdrawal’

Robert Newton

Papers

Molecular mechanisms of glucocorticoid action: what is important?

Evidence for Involvement of NF-κB in the Transcriptional Control of COX-2 Gene Expression by IL-1β ☆

Anti-inflammatory Effects of Resveratrol in Lung Epithelial Cells: Molecular Mechanisms

Separating Transrepression and Transactivation: A Distressing Divorce for the Glucocorticoid Receptor?

Human labour is associated with nuclear factor-κB activity which mediates cyclo-oxygenase-2 expression and is involved with the ‘functional progesterone withdrawal’